This video shows crocodiles feeding on a dead antelope. Hippopotamuses wander up to lick the crocodiles, which the crocs tolerate because the hippos are so much larger and stronger. At the end of the video, you can see a baby hippo gnawing on the back of a very patient crocodile.

Gauldar: "I'm not sure if it's been proven on what exactly the are getting out of licking them."

And the reason why we don't know is because the type of individual willing to walk into the middle of a bus-load of crocodiles *and* hippos to find out is also the type of person who doesn't live very long.